i dunno. brevity?
it is important to remember that your ccna is an "entry level" certification. while it will give you the knowledge with the cli (and presumably now the sdm), there is still a *lot* that isn't covered. my biggest complaint about the ccna is that it doesn't give enough "best practice" deployment information when you configure a device.
additionally - think of it like this:
what have you covered already in your ccna studies (as it pertains to switching)? i assume spanning-tree and vtp. both of these things can go extremely pear-shaped if someone connects a switch to your network and they negotiate trunks using bpdu's. how would you like to see a huge spanning-tree loop or maybe all of your vlan configuration information overwritten because you didn't set up the proper end-user vlan assignments on your closet switches. additionally, if i negotiate a trunk (and my pc can handle trunk frames) all of your vlan information can be sniffed and collected.
as a rule you *always* set the port type information on your switches and if the port serves and end user or is being unused, you set it to access mode (preferably on a non-existant vlan if its not in use). its just something you do according to best practices. have i seen networks that function with no port types being defined? sure. i've worked on networks that switches were just pulled out of the box and patched in. does that mean its right to do it that way? no.
"...if I in my north room dance naked, grotesquely before my mirror waving my shirt round my head and singing softly to myself..."